PERFUSION AND VENTILATION SCANS IN PATIENTS WITH EXTENSIVE OBSTRUCTIVE AIRWAY DISEASE - UTILITY OF SINGLE-BREATH (WASHIN) XE-133

The presence of extensive obstructive airway disease in many patients leads to an interpretation of intermediate or indeterminate probabilit y for pulmonary emboli using ventilation/perfusion lung scans. We obse rved that patients with extensive obstructive airway disease having pe rfusion abnormalities matching those on a single-breath xenon image us ually have a normal pulmonary angiogram. This study's objective was to further assess the utility of a single-breath image in evaluating pat ients with extensive obstructive airway disease and abnormal perfusion studies categorized as having intermediate or indeterminate probabili ty of pulmonary embolism in an attempt to decrease the number of nondi agnostic studies. Methods: We studied retrospectively 33 patients with extensive obstructive airway disease, with an abnormal perfusion scan s and no infiltrates on chest x-ray categorized as having intermediate or indeterminate probability of pulmonary embolism. We established th e presence or absence of matching ventilation and perfusion abnormalit ies by comparing perfusion scan and single-breath images. Results: Amo ng 25 patients with perfusion abnormalities matching the initial venti lation pattern on single-breath images, only 1 (4%) had pulmonary embo li as documented by pulmonary angiogram. Four out of the remaining 8 p atients with no matching perfusion and single-breath ventilation patte rn had pulmonary emboli (50%). Conclusion: Patients categorized by ven tilation/perfusion scintigraphy as having intermediate or indeterminat e probability for pulmonary emboli due to the presence of extensive ob structive airway disease can be further subclassified using single-bre ath ventilation pattern should be categorized as having low probabilit y for pulmonary embolism, regardless of the extent of the ventilation abnormalities.